How Well Do Dogs See in the Dark?
There has been an understanding for years that dogs can see better than humans at night. Is this correct? How well do dogs really see in the dark? Let’s look at the differences between human and canine vision.
Understanding Vision
The first part of understanding how well a dog can see in the dark is understanding how vision works. Obviously, we know that we open our eyes and look at something. The image gets transited to our brain. But what’s actually going on there?
Within our eyes, there is the retina. This is the light-sensitive portion of our eyes that does the transcoding of what we see. Within the retina, there are two different types of cells that distinguish what you see. These two cell types are called rods and cones. Rods help distinguish movement and low-light vision while cones distinguish color.
These two kinds of cells work together to create a full image of what you see. When you’re driving your car, for example, the rods in your eye make you aware of other drivers or pedestrians outside your car while the cones make you aware that you are following a car of a certain color. If you had less of one of these cells, you wouldn’t be able to see as well.
How do Humans See?
With both cells working together, you get a full image, but what if you had less cells of one type? Take for example people who are colorblind. For a typical person, they have cones that distinguish between 3 different colors. These cones also combine color in the retina so you can see a plethora of colors. But if you were missing cones for a certain color, you wouldn’t see that color.
This is what happens for some people who are color blind. The popular misconception about colorblind people is that they can’t see color at all. What actually happens is that they are usually missing cones of a certain color. This means they can still see the other two colors. So, a color-blind person is not actually blind to all colors, just some. They see muted tones of that color. This is actually much closer to how a dog sees.
How Do Dogs See?
Dogs can see two colors, violet and yellow. This means they can see any mix of these colors, but they cannot see green, yellow, orange, or red. Normally this isn’t a big deal as dogs can make up for this in other ways.
Dogs also have a wider set of eyes than humans do. What this translates to is a wider field of vision. Normally, prey creatures have eyes that are set wide so they have an easier time detecting any threats. Dogs are still predators though, so their eyes are set a little more forward, though a dog’s eyes are not as forward-facing as a human’s
Therefore, dogs can see a wider picture than humans, but they cannot see as clearly as humans. Our forward-facing eyes allow us to have better depth perception. Dogs are thought to have 20/75 vision. This means that dogs can see an object 20 feet away as clearly as a human standing 75 feet away from the same object.
So, dogs can’t see color as well as a person, and they can’t see as acutely as humans. But do dogs see better in the dark?
How Well Do Dogs See in the Dark?
Turns out, a dog can see a lot better than people in the dark. While dogs can’t see color as well as we can, they have other ocular adaptations that assist with night sight. These adaptations include:
- A larger pupil
- More rods than human eyes
- Having a lens that’s closer to the retina
- Having a tapetum
These four adaptations combine together to allow a dog to see dim light about five times better than a human can.
The dog’s larger pupil allows more light to enter the eye. Cats have an even larger pupil and thus can see even better than a dog could in low light. The fact that dogs have more rods in their eyes also helps them see better in the dark, and they can see movement better in the dark as well. Having their lens closer to the retina means light has an easier path into their eyes. While those three adaptations all mean better night sight, the last point is what makes a huge difference for dogs’ vision in the dark.
A tapetum is a small, mirror-like structure in the back of a dog’s eye. It’s the reason that you can often see a dog’s eyes at night or why a dog’s eyes in flash photographs seem to glow green. This mirror-like structure reflects light within the dog’s eyes and almost allows a dog to double process the light that does enter their eyes. While this really improves their night sight, it does come at a cost. The light reflecting in a dog’s eye also costs a dog some acuity.
While a dog has an advantage over humans when seeing at night, a human’s eyes are able to see much more clearly in daylight.